Hi,
I'm using a TI OMAP 3503 as SPI master and a Freescale MC1322x zigbee module, as SPI slave.
I find that I cannot perform perform 1 byte transfers. However, I can perform 2 byte, 4 byte and 16 byte transfers.
Is this a bug/limitation of the spi driver in linux-omap-2.6.32 kernel (latest arago TI PSP baseline for OMAP3)?
I modified the spidev_test.c program and I find that when sending data, I have to specific a minimum transfer length of 2, for a message.
If I specify an array size of 1, no transfer takes place.
I need 1 byte transfers to implement a firmware update program over SPI bus for the Freescale MC1322x zigbee module.
Would anyone have a code snippet or example that shows how to perform exactly 1 byte transfers using the spi bus on linux-2.6.32 kernel?
In the following example, if I set the firmware update file tranmit buffer size to 1, it doesnt work.
It works for 2, 4 and 16 byte transfers.
#define FIRMWARE_UPDATE_FILE_TRANSMIT_BUFFER_SIZE 16
static const char *device = "/dev/spidev3.0";
static const char *filename = "";
static uint8_t mode;
static uint8_t bits = 8;
static uint32_t speed = 4000000;
static uint16_t delay;
static void transfer_firmware_update_file(int fd)
{
FILE *file = NULL; // Pointer to a file descriptor.
unsigned long fileLength = 0; // Length of the file.
uint8_t tx [FIRMWARE_UPDATE_FILE_TRANSMIT_BUFFER_SIZE]; // SPI transmit buffer for firmware update file.
uint8_t rx [ARRAY_SIZE(tx)]; // SPI receive buffer for firmware update file.
int ret = -1; // Return result.
int count = 0; // Counter variable use for loops.
// Open the firmware update file in binary mode.
file = fopen(filename, "rb");
if(!file) {
fprintf(stderr, "Unable to open file %s\nPlease try again.\n", filename);
return;
}
// Get the length of the firmware update file.
fseek(file, 0, SEEK_END);
fileLength = ftell(file);
rewind(file);
#if (DEBUG)
// Display the size of the firmware update file
fprintf(stdout, "Size of the firmware update file = %ld bytes\n", fileLength);
// Display the size of the transmit buffer.
fprintf(stdout, "Size of the array for the firmware update file transmit buffer = %d\n", ARRAY_SIZE(tx));
// Display the size of the receive buffer.
fprintf(stdout, "Size of the array for the firmware update file receive buffer = %d\n", ARRAY_SIZE(rx));
#endif
// Initialize the SPI message transfer object
struct spi_ioc_transfer tr = {
.tx_buf = (unsigned long)tx,
.rx_buf = (unsigned long)rx,
.len = 0,
.delay_usecs = delay,
.speed_hz = speed,
.bits_per_word = bits,
};
// Initialize firmware update file transmit and receive buffers.
memset(tx, 0, sizeof(tx)); // Initialize all elements of the firmware update file transmit buffer to zero.
memset(rx, 0, sizeof(rx)); // Initialize all elements of the firmware update file receive buffer to zero.
// Message Sequence 02: Read the contents of the firmware update file in blocks and transmit it over the SPI bus.
while (ret != 0) {
// Read contents of the firmware update file into the transmit buffer. For binary file I/O, use fread and fwrite.
ret = fread(tx, 1, ARRAY_SIZE(tx), file);
// If we have no more bytes to read, exit the loop.
if (ret == 0) break;
// Update the SPI message transfer length.
tr.len = ret;
#if (DEBUG)
// Debug: Print out the contents of the transmit buffer array.
fprintf(stdout, "Number of elements read from the firmware update file into the transmit buffer = %d\n", ret);
fprintf(stdout, "\nDisplaying the contents of the transmit buffer\n");
for (count = 0; count < ret; count++) {
if (!(count % ret))
puts("");
printf("%.2X ", tx[count]);
}
#endif
// Send the SPI message payload.
if (ioctl(fd, SPI_IOC_MESSAGE(1), &tr) == 1)
pabort("Error: Cannot send spi message containing the firmware update file payload");
#if (DEBUG)
// Debug: Print out the contents of the receive buffer array.
fprintf(stdout, "\n\nDisplaying the contents of the receive buffer\n");
for (count = 0; count < ret; count++) {
if (!(count % ret))
puts("");
printf("%.2X ", rx[count]);
}
puts("");
fprintf(stdout, "\nNumber of bytes received = %d bytes\n\n", ret);
#endif
}; // end-of-while-loop
// Close the file handle.
if(file) {
fclose(file);
file = NULL;
fileLength = 0;
}
}
Best regards,
Elvis Dowson
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